Fire door assembly

ABSTRACT

A fire door assembly for automatically closing an opening in a wall in response to a predetermined condition has two or more door panels, a connection system for connecting a side edge of one of the door panels to an adjacent side edge of the other door panel in an edge-to-edge relationship, and flame break barriers interposed between the side edges of the panels and the connection system to provide a flame-resistant barrier between the core of each panel and the connection system. Tie bars are secured to the top and bottom edges of the panels to reinforce the edge-to-edge connection. A support system for the door has a track that is free from all external interference to allow free passage of suitably configured rollers.

This invention relates to fire doors, and more particularly to aprefabricated and partially assembled metal fire door assembly whichminimizes installation time and reduces maintenance

Many problems are present when a fire door is used for automaticallyclosing an opening in a wall. A primary concern is to assure that overthe passage of considerable lengths of time the door will still closesmoothly and efficiently.

Another problem that is prevelant in the installation of a fire doorassembly is the fact that an effective and efficient fire door normallyhas considerable mass, dependent upon the size of the opening in thewall. This creates difficulties in shipping and in the subsequentinstallation of the fire door assembly.

The present invention solves the aforementioned problems. The doorassembly is shipped in an easily manageable assembly kit. The assemblykit is such that a minimal number of assembly steps are required toinstall the fire door. This is achieved by pre-welding andpre-installing as many features of the fire door as possible while stillmaintaining a readily portable kit assembly. The kit comes with two ormore interconnectable hollow panels. A flame break channel isprefabricated within the panels to prevent the spread of fire fromwithin a panel cavity. By panelizing the door assembly, shippingoperations and the subsequent installation of the fire door assembly isgreatly facilitated. All installation steps require nothing more thanthe snapping together of parts or the attachment of bolts. No welding orother installation steps are necessitated.

Applicant's invention also provides an automatic closing system that isresponsive to an elevated temperature with respect to room temperature.The automatic closing system may not be used for a considerable lengthof time. When such need arises, the closing system must be functional.This is achieved in applicant's invention by ensuring that all movingparts of the automatic closing system are protected from obstruction.

It is an object of the present invention to provide a fire door assemblyin prefabricated and partially assembled panel sections which can beeasily transported and connected at the installation site to form thedoor with minimal installation time.

It is a further object of the present invention to provide a fire doorassembly having panel sections which will satisfy the requirements andstandards for preventing the spread of fire from within a panel cavity.

Another object of the present invention is to provide an automaticclosing system for a metal fire door assembly that remains operablethrough extended periods of time.

Yet another object of the present invention is to provide a completefire door assembly kit including adjustable support means, fire doorpanel sections, an edge-to-edge panel connection system, and anautomatic closing system.

The assembly embodying the present invention comprises at least twohollow door panels, means for lockably interconnecting the panels inadjacent edge-to-edge relationship, top and bottom tie bar assembliesfor rigidly securing the panels in the edge-to-edge relationship, meansfor preventing the spread of fire from within a panel cavity, means forslidably supporting the interconnected panels, and means forautomatically closing the interconnected panels in response to anelevated temperature with respect to room temperature.

In the illustrative embodiment, the automatic closing device includes adouble sheave, a single sheave, a counterweight that has a sufficientmass to pull the door closed and hold it closed in the event of fire,and a fuse link device that is temperature dependent and linked to thepulley system in such a manner that it will release the counterweightupon the occurrence of a critical elevation of temperature. A supportsystem for the door panels includes a track constructed in such a mannerthat its inner channel is free from all external interference to allow afree passage of suitably configured rollers from which the door assemblyis hung.

While the features of the present invention can be employed in manyenvironments, particular advantage is enjoyed in the construction ofvery large fire door assemblies because the individual sections can beeasily transported to the installation site prior to construction intothe final product. The on-site construction is simplified greatly by thepresent invention, since no multi-element fastener components are neededin the field for connecting the panels together. The assembly kit alsoprovides a reliable means for closing the door assembly automatically atany time in the event of fire.

Other features and advantages of the present invention will becomeapparent in view of the following detailed description of one embodimentthereof exemplifying the best mode of carrying out the invention aspresently perceived, which description should be considered inconjunction with the accompanying drawings in which:

FIG. 1 is a front elevational view of a fire door assembly embodying thepresent invention;

FIG. 2 is an exploded perspective view, partly broken away andcross-sectioned, of a fire door panel connection system including tiebar and flame-break assemblies embodying the present invention;

FIG. 3 is a cross-sectional view of the panel connection system shown inFIG. 2, taken generally along section lines 3--3 of FIG. 1;

FIG. 4 is a cross-sectional view, partly broken away, of the fire doorassembly shown in FIG. 1, taken generally along section lines 4--4 inFIG. 1; and

FIG. 5 is a top elevational view, partly broken away andcross-sectioned, of the door assembly of FIG. 1.

Referring now to FIG. 1, a completely constructed metal fire doorassembly 2 embodying the present invention is shown. The assembled door4 is slidably supported on a box track 6 by use of 4-wheel ball bearinghangers 8. The box track 6 is mounted to the wall by use of adjustablewall angle brackets 10 and track brackets 11. The adjustable wall anglebrackets 18, 20 located at the distal and proximal ends 12, 16 of boxtrack 6 have track blinds 14, 22 for limiting travel of the hangers 8along box track 6. Maximum travel of the assembled door 4 along boxtrack 6 can be defined by the position of optional end stops 24, 25 (notnecessarily used with the fire door assembly as the sheaves 30, 32 canbe used as alternate stops) located on the floor in a line parallel andplanar with the box track 6. The plane of travel of the assembled door 4is restricted by a concealed stay roller 26 that is equidistant from endstops 24, 25 and located in a line parallel and planar with the boxtrack 6.

To facilitate the automatic closing of door 4 along box track 6, themetal fire door assembly 2 includes a pulley system 28. The pulleysystem 28 includes a double sheave assembly 30 located at or near theproximal end 12 of the box track 6, a single sheave assembly 32 locatedat or near the distal end 16 of box track 6, and a counterweight 34located in a weight box 38 and suspended from a pulley cable 36. Thepulley cable 36 is threaded around the single sheave 32 and doublesheave 30 such that the counterweight 34 hangs freely within the weightbox 38. The other end of the cable 36 is attached to a fuse link device39 that is temperature-dependent and extends through the wall so thatthe fuse can respond to temperature variations on either side of thewall. An additional fuse link 39 is also provided in the center of theopening.

In operation, the fuse link device 39 breaks upon a predetermined risein temperature releasing the counterweight 34 which pulls the cable 36until a repair link 15 in the cable 36 frictionally engages a cablebracket 17 which is rigidly attached to a four-wheel roller 8. The cable36 in turn begins to pull the door 4 along the track 6 as thecounterweight 34 descends in the weight box 38. The counterweight 34 hasa mass sufficient to pull the door completely closed and hold it closed.

Referring to FIGS. 1 and 2, the door panels 44, 46 have a structuralcore 54 of resin-impregnated kraft honeycomb 48, shown in FIG. 2, with18 or 20 gauge, cold roll, galvanized or aluminized steel skins 50, 51,and 52, 53 bonded to core 54 under pressure. The orientation of thehoneycomb core 48 within the panels 44, 46 is such that the longitudinalaxis of the core 48 is at right angles to the skin 50, 51 and 52, 53 ofpanels 44, 46. Panel 44 has flush pulls 56 located on surfaces 52, 53 ofthe panel 44 at a height convenient to facilitate manual operation ofthe door 4. The flush pulls 56 are factory installed to minimize thenumber of asssembly steps necessary to erect the door 4 duringinstallation. The lead edge 42 of panel 44 and the trail edge 60 ofpanel 46 are constructed of 14-gauge cold roll steel that is factorywelded to the panels 44, 46 to give the trail edge 60 and the lead edge42 an armor edge finish.

Referring now to FIGS. 2 and 3, the two panels 44, 46 are interconnectedby an edge-to-edge connection system 62. Once the panels 44, 46 areinterconnected, tie bars 61 are attached over the top and bottom of thesplice joint 65 to rigidly secure the panels 44, 46 in theirinterconnected configuration. In the preferred embodiment, theedge-to-edge connection system is the same as that disclosed inapplication Ser. No. 306,002, filed Sept. 28, 1981, which is assigned tothe same assignee as this application.

The edge-to-edge connection system 62 includes vertical edge members 68which are generally U-shaped in cross section and are connected to theabutting vertical edges 70 and 72 of the panels 46 and 44, respectively.Each vertical edge member 68 includes side sections 69 which engage thesurfaces 50, 51 and 52, 53 of the panels 44 and 46. Each vertical edgemember 68 also includes a vertical plate section 76 which engages andextends along the vertical edge 70 and 72 of the panels 46 and 44,respectively. Preferably a vertical edge member 68 fits into the edge70, 72 of each panel 44, 46 so that the outer surfaces 50, 51 and 52, 53extend over and conceal the side sections 69. The vertical plate section76 extends 3/16 inch out past edges 70 and 72 so 3/16 inch of 69 isexposed. The outer surfaces 50, 51 and 52, 53 and side sections 69 arethen spot-welded to each other to provide a connection therebetween. Thevertical extension of outer surfaces 50, 51 and 52, 53 is sufficient tosnugly accommodate a top recess channel 138 such that the side sections139 of each channel 138 are flush with the top horizontal edges of outersurfaces 50, 51 and 52, 53. The recess channel 138 is secured to theouter surfaces 50, 51 and 52, 53 by conventional means such as welding.

The vertical plate section 76 of each vertical edge member 68 includesan alternating series of spaced-apart protuberances 80 and openings 82.The distance between each successive protuberance 80 and opening 82 isgenerally the same. Each protuberance 80 includes a generallytrapezoidal-shaped aperture which is formed by two angular side sections192 and an end section 194. The protuberances 80 project outwardly at agenerally right angle to the vertical edges 70 and 72 of the panels 46,44, respectively, to provide openings 84.

The alternating relationship of the protuberances 80 and the openings 82on the vertical edge 72 of one of the panels 44 is generally opposite tothe alternating relationship of the protuberances 80 and the openings 82on the vertical edge 70 of the other panel 46 so that when the edges 70and 72 are abutted, protuberances 80 along the vertical edge 70 of panel46 are received in the openings 82 along the vertical edge 72 of panel44, and protuberances 80 along the vertical edge 72 of panel 44 arereceived in the openings 82 along the vertical edge 70 of panel 46. Inabutting edge-to-edge relationship, the openings 84 of all of theprotuberances 80 are vertically aligned between the edges 70 and 72.

The vertical edges 70 and 72 are interlocked by a vertical lockingmember 86 which is generally H-shaped in cross section. The H-shapedlocking member includes two opposed side sections 88 and a web section90 therebetween. The side sections 88 and web section 90 are constructedfrom two vertical panels 92 which form the outer surface of the sidesections 88 and two generally U-shaped vertical channel members 102which are connected to each other and to the vertical panels byconventional means such as welding. The two U-shaped vertical channelmembers 102 form elongated vertical channels 104 which open in opposeddirections for receiving the edge members 68 along the vertical edges 70and 72 of panels 46 and 44, respectively.

The web section 90 of the locking member 86 includes a series ofspaced-apart windows 106. The distance between each of the windows 106corresponds generally to the distance between the protuberances 80 andopenings 82 along the vertical edge members 68. Windows 106 provide agateway for allowing passage of the protuberances through the webportion 90 of the locking member 86. Each window 106 includes adownwardly extending tongue or gate member 108 having a generallytrapezoidal shape. Each of the tongues 108 is inserted into an aperture82 formed by the protuberances 80 to interlock the panels 44 and 46. Itshould be noted that the tongues 108 have a maximum dimension 110 andminimum dimension 112. Apertures 84 in the protuberances 80 have alength which is slightly less than the maximum dimension 110 of thetongues 108 to provide a tight wedge-like connection between the tongues108 and apertures 84.

In using the edge-to-edge connection system, the panels 44 and 46 areinitially placed in adjacent edge-to-edge relationship with verticaledge 70 facing vertical edge 72. Locking member 86 is placed between thevertical edges 70 and 72 before they are butted together. Locking member86 is raised slightly upwardly so that the tongues or gate members 108in the web section 90 of the locking member 86 allow the protuberances80 along each vertical edge member 68 to pass through the windows 106 inthe web section 90. As the protuberances 80 are passed through thewindows 106, the edge members 68 along the edges 70 and 72 of the panels46 and 44, respectively, extend into the open channels 104 of thelocking member 86 so that the side sections 88 engage the surfaces 50,51 and 52, 53 of the panels 44 and 46. Once the protuberances have beeninserted through the windows 106 so that they engage correspondingopenings 82 in the opposite vertical edge member 68, the locking member86 is driven downward to force the tongues or gate members 108 into theapertures 84 formed in the protuberances 80. Because of the slightdifference between the maximum dimension 110 of the tongues 108 and thelength of the apertures 84, the protuberances 80 are slightly deformedwhen the locking member 86 is driven, so that the tongues 108 can beforced into engagement with the apertures 84.

The two panels 44 and 46 are securely and rigidly connected by theinterlocking of the protuberances 80 along each vertical edge member 68and the tongues or gate members 108 in the web section 90 of the lockingmember 86. Further, the side sections 88 of the locking member 86provide smooth surfaces on either side of the connection which blendwith the surfaces 50, 51 and 52, 53 of the panels 44 and 46 and concealthe splice 65 between the two panels 44 and 46. The side sections 88 incooperation with the surfaces 50, 51 and 52, 53 provide a seal along theconnection between the two panels 44 and 46. Upon engagement of theedge-to-edge connection system 62, tie bar assemblies 150 are securedover the top and bottom of the splice joint 65.

The top tie bar assembly 150 includes a tie bar 61 and a suitablyconfigured top recess channel 138 for connecting the tie bar 61 to thedoor panels 44 and 46. A bottom tie bar assembly 150 (shown in FIG. 4)includes the same elements as the top tie bar assembly 150.

A top door interlock 152 is connected to the top edges 71 and 73 of thepanels 44 and 46 and includes door lip or flange 160 which protrudesdownwardly in spaced relationship to the door 4. The lip 160 is suitablyconfigured to slidably engage an upwardly protruding wall lip or flange162 when the door 4 is in a closed position. The wall lip 162 isanchored to the wall opening by masonary bolts 164. The engagementbetween the door lip 160 and the wall lip 162 is such that it provides aflame barrier between the door 4 and the wall when door 4 is in a closedposition to prevent the spread of fire between the top of the door 4 andthe wall.

The tie bar 61 is centrally positioned with respect to its vertical axisover the edge-to-edge connection 65 of panels 44, 46 where it is rigidlyanchored by any conventional means, such as a plurality of bolts 158.The bight of the door interlock 152 is configured to extend over the toprecess channel 138. The inner cross-sectional dimension 154 of the doorinterlock 152 is slightly greater than the outer cross-sectionaldimension 156 of the top edges 71, 73 of panels 44, 46 to provide atight snug fit between the door interlock 152 and top edges 71, 73. Thedoor interlock 152 is held firmly in position on the top recess channel138 by the adjustable center posts 132 of the 4-wheel ball bearinghangers 8 when the posts 132 are bolted to and anchored in the panels44, 46, as best shown in FIG. 4. A reinforcement bar 140 is provided onthe plate section 142 of the recess channels 138.

Continuing to refer to FIGS. 2 and 3, the spread of fire from within apanel 44 or 46 is prevented by a flame-resistant U-shaped channel 114embodying the present invention. The flame-resistant U-shaped channel114 is received in the bight of the vertical edge member 68. The channel114 engages and extends along the side sections 69 of the vertical edgemember 68 so that the side sections 116 of the channel 114 are flushwith side sections 69. The side sections 116 of the channel 114 areslightly shorter than side sections 69 of vertical edge member 68 sothat a gap 115 is left between the front face 118 of the channel 114 andthe vertical plate section 76 of vertical edge member 68. The bights ofthe channels 114 open inwardly to the door panels 44, 46 along the edgesof the panels 44, 46 and receive the honeycomb core 54.

The side sections 116 of the flame-resistant U-shaped channel 114 extendin a direction opposite to the gap 115 between the front face 118 of thechannel 114 and the vertical plate section 76 of the vertical edgemember 68. The gap 115 that is left provides sufficient space to alloweasy operation of the edge-to-edge connection system. The channel 114 isconnected to the vertical edge member 68 by conventional means such aswelding. The honeycomb core 48 of panels 44, 46 is completely enclosedwithin the door cavity. Channels 114 provide flame break barriersbetween the honeycomb cores 48 of the panels 44 and 46 and the splice orconnection 65.

Referring now to FIG. 4, a first face 113 of the adjustable wall anglebrackets 10 is supported from a wall by a machine bolt 64 that extendsthrough the wall and is secured by a hex nut 120 and washer 122. Thetrack bracket 11 containing the box track 6 is rigidly attached to asecond face 121 of the adjustable wall angle brackets 10 by conventionalmeans such as a nut 128 and bolt 130. The track bracket 11 is generallyrectangular in shape and includes a longitudinal opening 129. The boxtrack 6 is somewhat rectangular in shape. The bottom surface 123 oftrack 6 includes flanges 124 extending inwardly and then upwardly toprovide a longitudinal opening 125 coinciding with opening 129. Theflanges 124 form spaced-apart generally U-shaped channels for the4-wheel ball bearing hangers 8 to freely slide along the box track 6.The box track 6 is secured inside the track bracket 11 by a trackhold-down clamp 126. The track hold-down clamp 126 is held in positioninside of the track bracket 11 by bolt 130 and nut 128 such that itclamps with a sufficient downward force to hold the box track 6 withinthe track bracket 11.

The track hold-down clamp 126 is positioned between the box track 6 andthe track bracket 11. In the eventuality that the bolt 130 and nut 128work loose over a period of time, there is no danger of the clamp 126,the bolt 130, or nut 128 becoming positioned in such a manner that itwould restrict the four-wheel ball bearing hanger 8 from freely slidingalong the box track 6. Slots 127 in the second faces 121 of theadjustable wall angle brackets 10 permit adjustment of the track bracket11 and box track 6 relative to the wall to help prevent binding betweenthe wall and the assembled door 4.

The 4-wheel ball bearing hangers 8 have an adjustable center post 132.One end of the adjustable center post 132 is connected to the wheels 134of the hangers 8. The other end of the center post 132 is anchored tothe door interlock 152 and the top recessed channel 138. In operation,the adjustable center post 132 may be adjusted as needed to providesufficient ground clearance for the door assembly 4 to travel freelyalong box track 6.

The concealed stay roller 26 is secured to the ground by an adjustablehex nut sleeve anchor 144. The concealed stay roller 26 is completelyenclosed within the bottom recessed channel 138 of panels 44, 46. Thedoor is adjusted by the adjustable center post 132 so that the topportion 148 of the concealed stay roller 26 does not rub, bind, or comein contact with the vertical plate section 142 of bottom recessedchannel 138 or with tie bar 61.

FIG. 5 shows the optional adjustable end stops 24, 25. The end stops 24,25 are L-shaped with an arcuate outer surface 161 and a right-angledinner surface 163. End stop 24 snugly receives the lead armor edge 136of panel 44. Both end stops 24 and 25 have a plurality of openings 165that permit adjustment relative to the door 4. The stops 24, 25 aspreviously stated are not necessarily used with the fire door assembly 2as the sheaves 30, 32 can be used as stops.

Upper and lower binders 172 are attached to the wall by use ofconventional means such as bolts and nuts. The binders are configuredsuch that when their faces 174 are secured to the wall, angled portions176 and 182 form upper and lower channels with the wall. As the doorcloses, the lead armor edge 136 of panel 44 is guided by portions 182 ofupper and lower binders 172 into the channels.

The trail edge 60 of the door 4 includes a side door interlock 184. Thedoor interlock 184 includes a lip or flange 185 in spaced relationshipto the surface 51 of panel 46. Lip 185 is suitably configured toslidably engage a protruding wall lip 186 when the door 4 is in a closedposition. The seal between the side lip 184 and the protruding wall lip186 is such that it effectively closes the periphery between the door 4and the wall when door 4 is in a closed position to provide a side flamebarrier between the door 4 and wall.

In use, the door assembly 2 is manufactured in such a manner as tominimize installation time and reduce the maintenance required to keepthe assembled door operating smoothly and trouble-free. By utilizing theabove-described kit, all that is necessary to erect and install the doorassembly 2 is a number of easily performed installation steps. Theadjustable wall hanger brackets 10 are positioned and secured to thewall above the opening to be closed. The track brackets 11 are securedto the wall angle brackets 10. The box track 6 is positioned and securedwithin the track brackets 11 by the track hold-down clamps 126. Doorpanels 44 and 46 are connected to each other using the edge-to-edgeconnection system 62 which includes flame-resistant channels 114.Depending upon the size of the opening to be closed, any number ofpanels can be joined together using a plurality of edge-to-edgeconnection systems 62. After the panels 44 and 46 are connected, tiebars 61 are installed within the recessed channels 138 to rigidly securethe edge-to-edge connection system 62 in a locked configuration. The topdoor interlock 152 is slid into position, and the four-wheel ballbearing hangers 8 are positioned and secured on the assembled door 4.The door can then be hung from the box track 6. When hanging the door 4,the concealed stay roller 26 is positioned in the bottom recess channel138 by swinging the assembled door 4 out away from the wall far enoughto slide the concealed stay roller 26 into the channel 138. The door maythen be swung back towards the wall and the concealed stay roller 26secured by use of the adjustable hex nut sleeve anchor 144. Travel ofthe door 4 along box track 6 is restricted so that when the door 4 is ina closed position the side door interlock 184 of trail edge 60 and theupper door interlock 152 snugly engage the wall lips 160 and 186 so asto effectively seal the periphery between the door 4 and the wall.

Next, the pulley system 28 is installed. The sheave assemblies 30 and 32are positioned and secured and the cable 36 is rigged to thecounterweight 34 and the fuse link device 39 so that upon the breakageof the fuse link device 39 the counterweight 34 will descend in theweight box 38 and pull the door 4 to a closed position. Upon completionof this easy step-by-step installation of the fire door, very littlemaintenance is required to keep the door in operating condition.Maintenance can be limited to periodic inspections to be certain thatall parts are functioning properly and freely.

What is claimed is:
 1. A fire door assembly for closing an opening in awall, the door assembly comprisingat least two panels having edges to beconnected, interconnecting means for connecting an edge of one of thedoor panels to an adjacent edge of the other door panel in edge-to-edgerelationship, flame-resistant means providing a flame barrier betweensaid interconnecting means and the edges of the panels, track means forslidably supporting the interconnected panels, and mounting means formounting the track means to the wall above the opening.
 2. The assemblyof claim 1, further comprising a pair of tie bars for reinforcing theconnection between the two panels, means for mounting the tie bars tothe panels, generally transverse to the connected edges such that eachtie bar extends over the connection between the panels.
 3. The assemblyof claim 1 wherein the interconnecting means includes a pair ofcontinuous U-shaped strips, each strip being fixed along the edge of oneof the door panels to be connected, each strip including a plurality ofspaced-apart protuberances projecting away from the edge to which thestrip is fixed, each protuberance having a first contact surface facingtoward the edge to which the strip is fixed, and locking meansinterposed between the pair of strips, the locking means including alinear plate having a plurality of apertures, means in each apertureproviding a second contact surface for engagement with the first contactsurface of a protuberance to prevent separation of the edges and whereinthe flame-resistant means includes a pair of continuous channels, eachchannel being interposed between a strip and the edge to which the stripis fixed such that the channel extends into the bight of the strip toprovide a flame-resistant barrier between the strip and the edge.
 4. Theassembly of claim 2 wherein the flame-resistant channels are generallyU-shaped, each strip and channel fixed to the edge including acontinuous surface in parallel relationship to the edge, the continuoussurfaces of each corresponding strip and channel being in spacedparallel relationship to each other.
 5. A fire door assembly for closingan opening in a wall, the door assembly comprising at least two doorpanels, each door panel having a top edge, a bottom edge, and sideedges, interconnecting means for connecting a side edge of one of thedoor panels to an adjacent side edge of the other door panel inedge-to-edge relationship, the interconnecting means including a pair ofcontinuous U-shaped strips, each strip being fixed along the side edgeof one of the door panels to be connected, each strip including aplurality of spaced-apart protuberances projecting away from the sideedge to which the strip is fixed, each protuberance having a firstcontact surface facing toward the side edge to which the strip is fixed,locking means interposed between the pair of strips, the locking meansincluding a linear plate having a plurality of apertures, means in eachaperture providing a second contact surface for engagement with thefirst contact surface of a protuberance to prevent separation of theside edges, flame-resistant means providing a flame barrier between theinterconnecting means and the interconnected side edges, theflame-resistant means including a pair of continuous channels, eachchannel being interposed between a strip and the side edge to which thestrip is fixed such that the channel extends into the bight of the stripto provide a flame-resistane barrier between the strip and the sideedge, track means for slidably supporting the interconnected panels, andmounting means for mounting the track means to the wall above theopening.
 6. The assembly of claim 5 wherein the flame-resistant channelsare generally U-shaped, each strip and channel fixed to the side edgeincluding a continuous surface in parallel relationship to the sideedge, the continuous surfaces of each corresponding strip and channelbeing in spaced parallel relationship to each other.
 7. The assembly ofclaim 6, further comprising a pair of tie bars for reinforcing theconnection between the two panels, means for mounting a first tie bar tothe top edges of both panels, and means for mounting a second tie bar tothe bottom edges of both panels, the first and second tie bars extendingalong the top and bottom edges, respectively, over the connectionbetween the panels.
 8. A fire door assembly for closing an opening in awall including means for automatically closing the door in response to apredetermined temperature, the door asembly comprising at least two doorpanels, each door panel including a top edge, a bottom edge, and sideedges, interconnecting means for interconnecting the side edge of one ofthe door panels to an adjacent side edge of the other door panel inedge-to-edge relationship, the interconnecting means including a pair ofsubstantially continuous U-shaped strips, each strip being fixed alongthe side edge of one of the panels to be connected, each strip includinga plurality of spaced-apart protuberances projecting away from the sideedge to which the strip is fixed, each protuberance having a firstcontact surface facing toward the side edge to which the strip is fixed,locking means interposed between the pair of strips, the locking meansincluding a linear plate having a plurality of apertures, means in eachaperture providing a second contact surface for engagement with thefirst contact surface of a protuberance to prevent separation of theside edges, flame-resistant means providing a flame barrier between theinterconnecting means and the interconnected side edges, theflame-resistant means including a pair of substantially continuousU-shaped channels, each channel being interposed between a strip and theside edge to which the strip is fixed such that the channel extends intothe bight of the strip, track means for slidably supporting theinterconnected door panels, mounting means including at least one trackbracket for containing the track means and retaining means for retainingthe track means within the track bracket, the retaining means includinga spring interposed between the track bracket and the track means, saidspring biasing the track means into frictional engagement with the trackbracket, and interlock means for interlocking the door panels and thewall, the interlock means including a first flange extending at leastpartially along the periphery of the opening and a second flangeextending along the top edge and at least one side edge of theinterconnected panels, the second flange being received in the firstflange to provide a flame barrier between the door panels and the wallwhen the door is closed.
 9. A fire door assembly for closing an openingin a wall, comprising at least two door panels, each door panelincluding a substantially continuous strip fixed along one of its edgesand a channel providing a flame barrier between the strip and the edgeto which the strip is fixed, each strip including a plurality ofspaced-apart protuberances projecting away from the side edge to whichit is fixed, each protuberance having a first contact surface facingtoward the side edge to which the strip is fixed, a linear plate havinga plurality of apertures, means in each aperture providing a secondcontact surface for engagement with the first contact surface of aprotuberance to connect the door panels in edge-to-edge relationship, atleast one track housing, means for mounting the housing to the wallabove the opening, a track in the track housing for supporting theconnected doors, and retaining means for biasing the track intofrictional engagement with the housing to retain the track in thehousing.
 10. A fire door assembly for closing an opening in a wall, thedoor assembly comprisingat least two door panels having edges to beconnected, interconnecting means for connecting an edge of one of thedoor panels to an adjacent edge of the other door panel in edge-to-edgerelationship, and flame-resistant means providing a flame barrierbetween said interconnecting means and the edges of the panels.
 11. Theassembly of claim 10 wherein the interconnecting means includes a pairof continuous U-shaped strips, each strip being fixed along the edge ofone of the door panels to be connected, each strip including a pluralityof spaced-apart protuberances projecting away from the edge to which thestrip is fixed, each protuberance having a first contact surface facingtoward the edge to which the strip is fixed, and locking meansinterposed between the pair of strips, the locking means including alinear plate having a plurality of apertures, means in each apertureproviding a second contact surface for engagement with the first contactsurface of a protuberance to prevent separation of the edges and whereinthe flame-resistant means includes a pair of continuous channels, eachchannel being interposed between a strip and the edge to which the stripis fixed such that the channel extends into the bight of the strip toprovide a flame-resistant barrier between the strip and the edge. 12.The assembly of claim 11 wherein the flame-resistant channels aregenerally U-shaped, each strip and channel fixed to the edge including acontinuous surface in parallel relationship to the edge, the continuoussurfaces of each corresponding strip and channel being in spacedparallel relationship to each other.
 13. The assembly of claim 10,further comprising a pair of tie bars for reinforcing the connectionbetween the two panels, means for mounting the tie bars to the panels,generally transverse to the connected edges such that each tie barextends over the connection between the panels.
 14. The assembly ofclaim 13 further comprising track means for slidably supporting theinterconnected door panels, mounting means including at least one trackbracket for containing the track means, and retaining means forretaining the track means within the track bracket, the retaining meansincluding a spring interposed between the track bracket and the trackmeans, said spring biasing the track means into frictional engagementwith the track bracket.
 15. The assembly of claim 14 further comprisinginterlock means for interlocking the door panels and the wall, theinterlock means including a first flange extending at least partiallyalong the periphery of the opening and a second flange extending alongthe top edge and at least one side edge of the interconnected panels,the second flange being received in the first flange to provide a flamebarrier between the door panels and the wall when the door is closed.